Polybius, in his account of the geography of Europe, says he passes over the ancient geographers but examines the men who criticise them, namely, Dicaearchus, and Eratosthenes, who has written the most recent treatise on Geography; and Pytheas, by whom many have been misled; for after asserting that he travelled over the whole of Britain that was accessible Pytheas reported that the coast-line of the island was more than forty thousand stadia, and added his story about Thule and about those regions in which there was no longer either land properly so‑called, or sea, or air, but a kind of substance concreted from all these elements, resembling a sea-lungs131 — a thing in which, he says, the earth, the sea, and all the elements are held in suspension; and this is a sort of bond to hold all together, which you can neither walk nor sail upon. Now, as for this thing that resembles the sea-lungs, he says that he saw it himself, but that all the rest he tells from hearsay. That, then, is the narrative of Pytheas, and to it he adds that on his return from those regions he visited the whole coast-line of Europe from Gades to the Tanaïs.